https://stackoverflow.com/questions/53391878 - Version 2

CSharp · Console

/Program.cs

using System;
using System.Collections.Generic;
using Newtonsoft.Json;
					
public class Program
{
	public static void Main()
	{
	    string json = @"[{""Name"":""Joe Schmoe""}]";
		
		List<Person> people = JsonConvert.DeserializeObject<List<Person>>(json);
		people.Add(new Person { Name = "Jane Doe", Birthday = new DateTime(1988, 10, 6) });
		json = JsonConvert.SerializeObject(people, Formatting.Indented);
		Console.WriteLine(json);
	}
}

public class Person  // Version 2
{
    public string Name { get; set; }
    public DateTime? Birthday { get; set; }
}